Published in Climatic Change 59: 5-31, 2003 Climatic change in mountain regions: a review of possible impacts Martin Beniston Department of Geosciences University of Fribourg Switzerland Abstract This paper addresses a number of issues related to current and future climatic change and its impacts on mountain environments and economies, focusing on the “Mountain Regions” Chapter 13 of Agenda 21, a basis document presented at the 1992 United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro, and the International Year of the Mountains (IYM) 2002. The awareness that mountain regions are an important component of the earth’s ecosystems, in terms of the resources and services that they provide to both mountain communities and lowland residents, has risen in the intervening decade. Based upon the themes outlined in the supporting documents for IYM, this paper will provide a succinct review of a number of sectors that warrant particular attention, according to IYM. These sectors include water resources, ecosystems and biological diversity, natural hazards, health issues, and tourism. A portfolio of research and policy options are discussed in the concluding section, as a summary of what the IYM and other concerned international networks consider to be the priority for mountain environmental protection, capacity building, and response strategies in the face of climatic change in the short to medium term future. 1. Introduction In June 1992, the United Nations Conference on Environment and Development (UNCED, Rio de Janeiro) addressed a range of issues pertaining to sustainable development as a means of reducing human-induced environmental stress, in a document referred to as Agenda 21. Chapter 13 of this program is exclusively devoted to mountain regions and, for the first time, an official and explicit recognition that mountains and uplands are a major component of the global environment has emerged. Chapter 13 sets the scene by stating the role of mountains within the global ecosystem, and expresses serious concerns related to the decline in the general environmental quality of many mountains. A summarized version (UN, 1992) of Agenda 21/13 reads: “Mountains are important sources of water, energy, minerals, forest and agricultural products and areas of recreation. They are storehouses of biological diversity, home to endangered species and an essential part of the global ecosystem. From the Andes to the Himalayas, and from Southeast Asia to East and Central Africa, there is serious ecological deterioration. Most mountain areas are experiencing environmental degradation.” Significant orographic features occupy close to 25% of continental surfaces (Kapos et al., 2000) and, although only about 26% of the world’s population resides within mountains or in the foothills of the mountains (Meybeck et al., 2001), mountain-based resources indirectly provide sustenance for over half. Moreover, 40% of global population lives in the watersheds of rivers originating in the planet’s different mountain ranges. Mountains also represent unique areas for the detection of climatic change and the assessment of climate-related impacts. One reason for this is that, as climate changes rapidly with height over M. Beniston, 2001 Revised Draft - 1 - relatively short horizontal distances, so does vegetation and hydrology (Whiteman, 2000). As a consequence, mountains exhibit high biodiversity, often with sharp transitions (ecotones) in vegetation sequences, and equally rapid changes from vegetation and soil to snow and ice. In addition, mountains ecosystems are often endemic, because many species remain isolated at high elevations compared to lowland vegetation communities that can occupy climatic niches spread over wider latitudinal belts. Certain mountain chains have been referred to as “islands” rising above the surrounding plains (Hedberg, 1964), such as those in East Africa. In socio-economic terms, mountain landscapes attract large numbers of people in search of opportunities for recreation and tourism. However, the environmental stress imposed by growing numbers of tourists is placing an increasingly heavy burden on mountain resources (Godde et al., 2000) and, in many parts of the developing world in particular, on local communities. With the rapid industrialization and population growth that the 20th century has witnessed worldwide, the natural environment has undergone unprecedented changes. While the causal mechanisms of environmental and climatic change are numerous and complex, two factors can be highlighted to explain the increasing stress imposed by human interference on the natural environment: economic growth and population growth. The economic level of a country determines to a large extent its resource requirements, in particular energy, industrial commodities, agricultural products and fresh water supply. Rising population levels, on the other hand, can weigh heavily upon the resources available per capita, particularly in less affluent countries. Bearing these two factors in mind, environmental deterioration in mountains can be driven by numerous factors that include deforestation, over-grazing by livestock and cultivation of marginal soils. Mountain ecosystems are susceptible to soil erosion, landslides and the rapid loss of habitat and genetic diversity. In many developing countries, in part because of the degradation of the natural environment, there is widespread unemployment, poverty, poor health and bad sanitation (Price et al., 2000). Such concerns have prompted a number of research and policy initiatives that have acknowledged and highlighted the importance of mountain environments in environmental, economic, and social terms. Perhaps the most notable action, at least in terms of policy, has been the proclamation, by the UN General Assembly in 1998 (UN, 1998), of the year 2002 as the “International Year of the Mountains” (IYM), declaring that: “The aim of IYM is to ensure the well-being of mountain and lowland communities by promoting the conservation and sustainable development of mountain regions. FAO [the United Nations Food and Agricultural Organization], the lead agency for IYM, is working closely with UN and other organizations to make sure the broadest possible range of expertise is focused on reaching the goals of sustainable mountain development. One of IYM's goals is to raise awareness about the challenges in protecting mountain habitats and improving living standards in mountain communities.” The IYM is aimed at furthering ongoing actions and stimulating new initiatives related to the following sectors: x Natural resources, particularly climate, water, soils, biodiversity, and forests; x Resource use, namely water, agriculture, forestry, and mining; x Socio-economic issues, such as tourism, trade and transportation, people and culture, and financial mechanisms and strategies; M. Beniston, 2001 Revised Draft - 2 - x Integrated themes, with a focus on health and well-being, risks and hazards, watershed management, mountain protected areas, integrated mountain development, conflicts, and policies. In the general framework of IYM-2002, mountains indeed offer interesting research opportunities. In the remote mountain environments of high altitudes or latitudes, there is the potential for investigating the impacts of environmental change in the absence of direct or significant human interference. Furthermore, because of the latitudinal range and varying degree of continentality of mountains distributed around the globe, comparative analyses can be undertaken to assess the manner in which climatic change may lead to similarities – or differences – in the response of environmental and socio-economic systems to change. This paper will provide a brief review of climatic change, as it may influence different mountain regions of the world, with a focus on a number of impacts sectors considered to be important in the IYM framework, namely: x Water, snow and ice: because the hydrological cycle will be enhanced under warmer climatic conditions, the current distribution, seasonality, and amount of precipitation may undergo significant changes in various geographical regions. The consequences for river runoff are likely to affect not only the watersheds within the mountains themselves, but also in the lowland regions that are heavily dependent on this mountain resource; x Vegetation, forests, and biodiversity: biodiversity in mountain areas encompasses both natural and cultivated species; these systems are all sensitive to climatic factors and are likely to have different vulnerability thresholds according to the species, the amplitude, and the rate of climatic change. The preservation and enhancement of vegetation cover in natural, semi- natural, agricultural, forest, and agroforestry ecosystems is an essential factor in sustaining environmental health in mountains, in helping to avert natural hazards such as landslides through the upkeep of adequate vegetation cover, and in maintaining water quality; x Health: changing climates may lead to new distributions of vector-borne disease. A particularly interesting example in the context of mountains and uplands is the possible propagation of malaria as an indicator of climatic change. Regions that are today unfavorable for the development of the disease, which is in part climatically-driven, may open up to malaria in areas that would experience more favorable temperature and moisture conditions than today; x Tourism: over the last 25 years, tourism and recreation